Control device and program

A non-transitory storage medium encoded with a computer readable program which, when executed by a computer of control device, cause the computer to perform operations comprising:

• executing a control computation cyclically with a predetermined execution cycle, the control computation including:
• collecting input data from a field device;
• calculating output data based on the input data in accordance with a predetermined user program;
• and outputting the calculated output data,
• the computer including a database configured to store, in a time-series order, designated data among data managed by the control computation, the program causing the computer to perform
• writing data in the database with the same cycle as the execution cycle with which the control computation is executed cyclically, wherein
• the writing the data includes:
• constructing a reference record of the designated data;
• and
• constructing a differential record of the designated data when a predetermined condition is satisfied.